N-(dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1994-05-03 to 1994-05-06

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The study was conducted according to an appropriate OECD test guideline, and in compliance with GLP, and was considered to be reliability 1 (reliable without restrictions).

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

Cited as Directive 92/69/EEC, C.3

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: All concentrations at the start and end of the test in fresh and/or old media as applicable

- Sampling method: Not reported

- Sample storage conditions before analysis: Not reported

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Test media prepared by mixing for 18 h followed by filtration.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM

- Strain: 86.81.SAG

- Source (laboratory, culture collection): Institute for Water, Ground and Air Hygiene, Berlin (Germany)

- Age of inoculum (at test initiation): 3 days

- Method of cultivation: A pre-culture is produced from an original culture by super-inoculation three days before the test begins. From this culture the test cultures are inoculated at a density of about 20000 cells/ml.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

No data

Test temperature:

24+/-2ºC

pH:

8.5-9.3 at start of test

8.7-9.8 at end of test

Dissolved oxygen:

No data

Salinity:

Not applicable

Nominal and measured concentrations:

Target test substance concentrations were 1.4, 3.1, 6.4, 14, 31, 64 and  140 mg/L.  

The 72-hour values were 2.0, 2.7, 5.6, 11.9, 40.7, 66.4, and 151  mg/L. 

The geometric mean of analytical values at 0 and 72 hours deviated by <20% from that of the nominal  concentrations (except at the target concentration of 1.4 mg/L). 

The nominal concentrations were used to present and interpret the test results.

Details on test conditions:

TEST SYSTEM

- Test vessel:

- Type: open Erlenmeyer flasks

- Material: glass

- Aeration: none

- Initial cells density: 20000 cells/ml

- Control end cells density: 1130000 cells/ml

- No. of vessels per concentration (replicates): 5

- No. of vessels per control (replicates): 8

GROWTH MEDIUM

- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS

- Culture medium different from test medium: no

- Intervals of water quality measurement: start and end of test

OTHER TEST CONDITIONS

- Sterile test conditions: yes

- Adjustment of pH: no

- Photoperiod: continuous

- Light intensity and quality: 8000 Lux

EFFECT PARAMETERS MEASURED: Algae cell counts were made photometrically at 0, 24, 48 and 72 hrs.

- Determination of cell concentrations: spectrophotometer (absorption at 685 nm)

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2.2

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

7.5 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

7.5 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

50 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

2.7 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

2.7 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

19 mg/L

Nominal / measured:

nominal

Conc. based on:

other: test substance hydrolysis products

Basis for effect:

biomass

Details on results:

- Exponential growth in the control (for algal test): yes

Reported statistics and error estimates:

The ECx values were determined by Probit analysis. The NOEC was taken as the EC10 values.

Table 1. Results of analysis of test media

Nominal concentration (mg/L)	Measured concentration at the start of the test (mg/L)	Measured concentration at end of test (mg/L)	Concentration used to assess results (mg/L)
0 (Control)	-	-	-
1.4	2.0	2.0	1.4
3.1	4.0	2.7	3.1
6.4	7.8	5.6	6.4
14	13.9	11.9	14
31	32.4	40.7	31
64	70.4	66.4	64
140	148	151	140

Table 2. Test results

Test concentration (mg/L)	Mean cell concentration at t0 (cells/ml)	Mean cell concentration at t24 (cells/ml)	Mean cell concentration at t48 (cells/ml)	Mean cell concentration at t72 (cells/ml)
0 (Control)	20000	120000	370000	1130000
1.4	20000	100000	360000	940000
3.1	20000	120000	320000	870000
6.4	20000	120000	340000	990000
14	20000	100000	300000	710000
31	20000	70000	220000	430000
64	20000	50000	70000	80000
140	20000	40000	40000	40000

Validity criteria fulfilled:

yes

Conclusions:

A 72-hour EC50 value of 50 mg/L and a NOEC of 7.5 mg/L has been determined for the effects of the test substance on growth rate of Scenedesmus subspicatus. It is likely that the test organisms were exposed to the hydrolysis products of the substance.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2004-03-11 to 2004-03-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.5400 (Algal Toxicity, Tiers I and II) (January 2012)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Negative Control, 31, 63, 125, 250, 500 and 1000 mg/L

- Sampling method: Test concentrations were measured in each treatment at test initiation and at test termination.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Direct addition of test article to freshwater algal medium

- Controls: Freshwater Algal Medium (OECD 201)

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM

- Source (laboratory, culture collection): Original algal cultures were obtained from the University of Toronto Culture Collection, and had been maintained in culture medium at Wildlife International, Ltd., Easton, Maryland. Algal cells used in this test were obtained from Wildlife International, Ltd. cultures that had been actively growing in culture medium for at least two weeks prior to test initiation. The culture was last transferred to fresh medium three days prior to test initiation.

- Culture medium: The algal cells were cultured and tested in freshwater algal medium. Stock nutrient solutions were prepared by adding reagent-grade chemicals to purified Wildlife International, Ltd. well water. The test medium then was prepared by adding appropriate volumes of the stock nutrient solutions to purified well water (NANOpure® water). The pH of the medium was adjusted to 7.9 using 10% HCl and the medium was sterilized by filtration (0.22 μm) prior to use.

- Initial density: 10,000 cells/mL

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Post exposure observation period:

None

Test temperature:

23.6 to 24.6 ºC

pH:

7.9 at test initiation

8.3 to 9.9 at test termination

Dissolved oxygen:

Not applicable

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: Negative Control, 31, 63, 125, 250, 500 and 1000 mg/L.

Measured concentrations:
Test concentrations declined to less than 70% of nominal at test termination. Consequently, the results of the study were based on Day 0 measured concentrations.

Details on test conditions:

TEST SYSTEM

- Test vessel: 250-mL Erlenmeyer flasks plugged with cotton stoppers containing 100 mL of test solution.

- Aeration: none

- Renewal rate of test solution (frequency/flow rate): static test

- Initial cells density: 10000 cells/mL

- No. of vessels per concentration (replicates): 3

- No. of vessels per control (replicates): 6


GROWTH MEDIUM

- Standard medium used: yes


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Freshwater algal growth medium (OECD 201) with NANOpure water (pH: 7.9)

- Culture medium different from test medium: no

- Intervals of water quality measurement: Start and end of test


OTHER TEST CONDITIONS

- Sterile test conditions: yes

- Adjustment of pH: no

- Photoperiod: Continuous

- Light intensity and quality: 3900 to 4700 lux, continuous cool-white fluorescent lighting


EFFECT PARAMETERS MEASURED: Cell densities measured at start of test and then at 24 hour intervals. Cell densities were used to determine effects on average-specific growth rate and biomass.


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

70 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

555 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 141-612

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

135 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

683 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 641-727

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

70 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

566 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 409-618

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

70 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

625 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 555-702

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

70 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 053 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: not calculable

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

522 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

> 1 053 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: not calculable

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

50 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 750 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: not calculable

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 684 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

44 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

Was control response satisfactory: Yes

Observations: There were no noticeable changes in cell morphology in any of the tested concentrations in comparison to the control.

Reported statistics and error estimates:

Statistical methods: Non-linear regression, linear interpolation and Dunnett's test

Table 1. Test results (cell densities in cells/mL)

Day 0 Measured  Concentration (mg/L)
          0 33     70     135    257    522    1053
0-Hour  10000  10000 10000 10000  10000  10000  10000
24-Hour  72000 75000 67000 67000 60000 51000 22000
48-Hour  396000 389000   345000 322000  263000  193000  44000
72-Hour  1780000 1700000 1680000 1090000 882000  995000  172000
96-Hour  4660000 4620000 4690000 4740000 3810000 3500000 570000

Table 2. Percent biomass/growth rate inhibition per concentration

         Day 0 Measured Concentration (mg/L)
                 33    70    135   257   522   1053
72-Hour Cell Density  4.6   5.8   39    51    44    90
96-Hour Cell Density  0.74 -0.70 -1.8   18    25    88
72-Hour Biomass       3.4   8.0   32    45    46    90
96-Hour Biomass       2.3   3.1   16    32    35    89
72-Hour Growth Rate   0.94  1.2   9.5   14    11    45
96-Hour Growth Rate   0.12 -0.11 -0.30  3.3   4.6   34

Validity criteria fulfilled:

yes

Conclusions:

A 72-hour EC50 value of >1053 mg/L and NOEC of 70 mg/L have been determined for the effects of the test on growth rate of Selenastrum capricornutum (new name: Pseudokirchneriella subcapitata) based on initial measured concentrations of the test substance. When expressed relative to geometric mean measured concentrations the equivalent values are >684 mg/L and 44 mg/L.

Description of key information

Algal 72 hr EC₅₀ 50 mg/l (nominal) (EU method C.3), read-across from a structurally related substance, 1,1,1,3,3,3-hexamethyldisilazane (CAS 999-97-3). The EC₅₀ is equivalent to 28 mg/l when expressed in terms of the silanol hydrolysis product, trimethylsilanol and 5 mg/l in terms of NH₃.

Algal 72 hr EC₅₀ >684 mg/l and NOEC 44 mg/l (geometric mean measured) (OECD 201), read-across from an analogous substance, trimethylsilanol (CAS 1066-40-6).

Algal 72 hour EC₅₀ >89 mg/l (nominal), read-across from an analogous, trimethoxy(vinyl)silane (CAS 2768-02-7). The EC₅₀ is equivalent to >64 mg/l when expressed in terms of the silanol hydrolysis product, vinylsilanetriol.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

44 mg/L

Additional information

There are no reliable algal inhibition data for N-(dimethylvinylsilyl)-1,1-dimethyl-1-vinylsilylamine, therefore good quality data have been read-across for the effects of two read-across substances: 1,1,1,3,3,3-hexamethyldisilazane (CAS 999-97-3), and trimethylsilanol (CAS 1066-40-6) based on structural similarity and production of ammonia, and structural similarity and log K_ow of the silanol hydrolysis product of the registered substance, respectively. In addition, reliable supporting data are presented for trimethoxy(vinyl)silane (CAS 2768-02-7) to demonstrate the low toxicity of the vinyl group.

 

The EC50 values of 50 (72 hr), >684 (72 hr) and >89 (72 hour) mg/l and NOECs of 7.5, 44 and ≥89 mg/l (nominal, measured and nominal respectively) have been determined for the effects of the read-across substances 1,1,1,3,3,3-hexamethyldisilazane (CAS 999-97-3), trimethylsilanol (CAS 1066-40-6) and trimethoxy(vinyl)silane (CAS 2768-02-7), respectively, on growth rate of Scenedesmus subspicatus (new name: Desmodesmus subspicatus) for the first two substances and on growth rate of Pseudokirchnerella subcapitata for trimethoxy(vinyl)silane. The trimethylsilanol (CAS 1066-40-6) study results are reported in terms of the geometric mean measured concentrations, due to the reduction in test substance recovery by the end of the test (<70%).

The data on trimethylsilanol (CAS 1066-40-6) are used to derive the PNEC for the silanol hydrolysis product, whereas the data for 1,1,1,3,3,3-hexamethyldisilazane (CAS 999-97-3) are used to establish the classification and labelling of the registered substance due to the presence of the ammonia hydrolysis product, which drives toxicity. The PNECs for ammonia are derived based on literature data.

For trimethylsilanol, a solution at 100 mg/l is predicted to contain >99.9% monomer. At loadings above about 500 - 1000 mg/l the concentration of the dimer is predicted to exceed its solubility, resulting in formation of a separate phase. During the algae test with trimethylsilanol, less than 20% growth inhibition was observed up to the 522 mg/l loading level and the EC₅₀ is considered to be above the highest concentration tested. In addition, the dimer that could be formed due to the condensation of two trimethylsilanol molecules is hexamethyldisiloxane (HMDS, CAS 107-46-0). HMDS is classified as Aquatic Acute 1 H400 and Aquatic Chronic 2 H411^[1] and therefore its presence may impact the toxicity results. However, the estimated concentration of HMDS is 0.04, 0.2, 0.3, 0.6 and 0.9 mg/l at 100, 200, 300, 400 and 500 mg/l of TMS respectively, and there was no reporting of undissolved test material or droplets being formed, which would otherwise clearly indicate the formation of HMDS. Furthermore, the log K_owof trimethylsilanol (1.62) is such that effects at relatively high loadings may be observed. Therefore, any condensation reactions that may have occurred did not significantly impact the results of the study and it is concluded that the study is considered to be reliable and sufficient for the assessment as part of the Weight of Evidence approach. This conclusion is supported by the analogous EC₅₀ results obtained in the two algal studies with TMS.

 

In view of the exposure regime and the fast hydrolysis rates of 1,1,1,3,3,3-hexamethyldisilazanethyldisilazane (CAS 999-97-3) and trimethoxy(vinyl)silane (CAS 2768-02-7) it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substances, trimethylsilanol and ammonia, and vinylsilanetriol and methanol, respectively.

 

1,1,1,3,3,3-Hexamethyldisilazane (CAS 999-97-3)

The results may be expressed in terms of concentration of the hydrolysis product, trimethylsilanol, by applying a molecular weight correction:

(MW of silanol = 90.2 / MW of parent = 161.4) * EC50/NOEC mg/l = 28 mg/l EC₅₀ and 4.2 mg/l NOEC

The results may also be expressed in terms of ammonia (NH3), by applying a molecular weight correction:

(MW of ammonia 17.03 / MW parent 161.4) * EC₅₀/NOEC mg/l = 5.3 mg/l EC₅₀ and 0.8 mg/l.

However, data with 1,1,1,3,3,3-hexamethyldisilazane are read-across for the purpose of classification and labelling and the relevant values are those determined in terms of the parent substance.

 

Trimethoxy(vinyl)silane (CAS 2768-02-7)

The results may be expressed in terms of concentration of the hydrolysis product, vinylsilanetriol, by applying a molecular weight correction:

(MW of silanol = 106.15 / MW of parent = 148.24) * EC₅₀ or NOEC value thus 106.15/148.24 * EC₅₀ of >89 mg/L and NOEC of ≥89 mg/L = EC₅₀ >64 mg/L and NOEC ≥64 mg/L as vinylsilantriol.

These values are read across to dimethylvinylsilanol without further correction.

 

Refer to the discussion in the Section 6 endpoint summary (Section 7.0 of CSR) for further discussion of the approach to chemical safety assessment for this registration substance. The justification for read-across can be found in IUCLID Section 13.

Ammonia 

Reliable short-term test results are available for ammonia sourced from the Environment Agency Proposed EQS for Water Framework Directive Annex VIII Substances: Ammonia (unionised) 2007. A five day EC₅₀ of 2.0 mg NH₃/l, and a 14 day LOEC of 3.0 mg NH₃/l has been reported for toxicity of ammonia to algae.

[1]https://echa.europa.eu/information-on-chemicals/cl-inventory-database/-/discli/notification-details/32082/948794